High-resolution remote sensors and equipments collected far more images than transmitted through limited-band downlink channels. There is a critical need for special target detection algorithm to select subset of the image collection effectively. An adaptive non-uniform rectangular segmentation and merging algorithm (ANURSM) is proposed to meet the requirement. The algorithm extracts coefficients corresponding to target-area from background in LL3 subband of wavelet-transformed images, and can be integrated with CCSDS-IDC (The Consultative Committee for Space Data Systems-Image Data Compression Recommended Standard) easily and seamlessly. Experiments have demonstrated that the algorithm can effectively reduce data volume and improve the quality of target areas in images.